The need in surgery and other areas to illuminate internal and hard to reach areas has long been recognized. Thomas Edison first used a miniature incandescent electric lamp to replace the wax candle as a source for such illumination. However, heat from such lamps has always posed a problem for surgical usage.
A major breakthrough occurred when fiber optics were used to convey light from a remote source of optical radiation to an area where illumination is needed. However, problems with illumination devices such as fiber bundles remain because of their bulk and lack of flexibility. The large minimum bend radius of fiber optics limits their ease of use. Exceeding the bend radius limit is a typical source of failure. Single fiber systems do not solve this problem and are even more prone to failure than bundles of fibers.
A further problem with conventional illumination sources is that the color temperature of incandescent lamps is so low (2,600-3,000.degree. K) that the reddish cast given off by the light diminishes the visibility of important physiological structures in surgical applications. This color rendering problem was partially solved in devices incorporating Xenon arc lamps as their source. The emission spectrum of Xenon provides a whiter illumination. A further problem with Xenon arc lamps exists, however, since they emit a large fraction of their total energy in the invisible infrared and ultraviolet wavelengths. This invisible waste energy part of the Xenon spectrum (both ultraviolet and infrared) ends up as heat. Excess heat is a serious problem in heat sensitive applications, such as many surgical applications, because of tissue dehydration, cooking, and burning, as well as adding to the heat load in operation rooms, which are typically air-conditioned. An additional disadvantage of Xenon arc lamps is that the power level required is typically too high to use an internal power source such as a battery.
Accordingly, the inventor has determined that it would be desirable to have an illumination device which is miniature, cool operating, and convenient to use, and which provides ergonomically correct lighting of scenes which are viewed directly.